Horizontal and vertical pull plate-lifting clamp



April 27, 1954 E. M. GARDNER 2,676,838

HORIZONTAL AND VERTICAL PULL PLATE-LIFTING CLAMP Filed March 2'7, 1952 2FIG.5

INVENTDR .clamp. .o.fDu further. object of; the inventionjs to provide aliftin qllainpiwh gh isadap e de ecta sure Patented Apr. 27, 1954 UNITEDSTATES wens HORIZONTAL AND VERTICAL PULL PLATE-LIFTING CLAMP EdwardMerrill Gardner, Brooklyn, N. Y., as-

signor to Merrill Brothers, New York, N. Y., a

corporation of New York Application March 27, 1952, Serial No. 278,864

9 Claims. (01. 294104) This invention relates to improvements in liftingclamps particularly adapted for gripping and lifting steel plates andother heavy articles presenting a relatively thin edge adapted to bereceived into the clamp.

The lifting clamp of the present invention is adapted to effect a suregrip on a steel plate, for example, when the lift or pull is vertical orhorizontal or at any angle in between, and constitutes' an improvementon the applicants Patent No. 2,393,101 granted January 15, 1946.

With respect to the lifting clamp disclosed in said patent, it has beenfound that this clamp works perfectly, regardless of the direction ofpull provided the short leg or jaw of the clamp is underneath the plate,but when the plate is lifted and then let down again, it is oftenlowered with the short leg or jaw of the clamp on top of the plate.Under these conditions, it has been found that in a number of cases, theclamp has released its grip on the plate and allowed the plate to fall,this being particularly true in handling plates of a thickness of aboutone fourth or less of the maximum capacity of the clamp.

7 In checking on the reasons for the release of the lifting clamp underthe conditions referred to above, it was found that the grippingpressure on the camisrelaxed and in some instances re- .sulting in theinadvertent release of the clamp from the plate. V

In the use of the clamp disclosed in said patent, it has also been foundthat at times the operator would attach theclamp to a plate somewhat outof the normal rangeof the lifting crane and so that a side pull would beappliedt o the a clamp. causing a severe bending and tensile strain onone of the eyes of the lifting shackle.

In some instances the misuse of the clamp in this way has caused oneside of the lifting shackle to stretch and rupture and the other side tobend and break, Whereas under normal conditions, the lifting shacklewould have an ample safety factor.

Having in mindthe foregoing, the primary object of the present inventionis to provide an improved lifting clamp which will be free 'of theweaknesses and ,defects encountered in tionwiththe; clamp referred to.above.

A further object of the. invention is to provide a lifting clamp forsteel plates and the like, which .is; adapted to. maintain a sure gripon the plate,

regardlessjof its thickness, the position of the g 7 ith respect to theplate, and the direction ,conneca side direction pull or a pull in anyother direc- According to theinvention the improved clamp, having astructure which avoids the difficulties referred to above, comprises aclamp body having spaced opposed depending portions between which thearticle to be lifted is held, a gripping pad on one of said dependingportions facing the other depending portion, a cam member, having anarcuate article-gripping surface, pivoted in the other depending portionwith its gripping surface facing toward the gripping pad, a leveragemeans for applying pressure to the cam member, including abell crankpivotally mounted in the body of the clamp with its inside angle facinggenerally toward the cam member, a connecting link in the cla-mpbody theends of which are respectively-pivoted to the cammember and to one armof the bell crank, and a liftin shackle connected to the other arm ofthe bell crank.

With this construction has been found that pressure will always bemaintained on the cam member to grip the plate being handled withoutbeing released, since the pivot point of the arm of the bell crank towhich the lifting shackle is connected can never come in line with thepivot of the bell crank and the direction of pull or lift applied to theclamp. In this construction,

the end of .the bell crank arm to which the liftting shackle is attacheis always well within the body of the clamp, and, in accordance with apreferred construction, that arm of the bell crank extendsgenerallytoward the center of the clamp,

is forked and spansa short shackle link to which it is pivoted, theshort shackle-connecting link being in turn spanned by the liftingshackle and pivoted thereto, I he short shackle-connecting link providesan intermediate link connection belifting shackle;thisprojecting portionhaving at least two, important functions.

t provides an extended bearingsurface in the fork of the lifting shacklewhich increases the strength of the 7 connection between, the liftingshack-1e and the bell crank; and: provides amember having a point .orend which canbestruck with ahammer to break loose the. grip of the cammember on the plate when it is desiredto release. the clamp. I

The improved lifting clamp of the present invention provides a sure gripfor steel plates and similar articles, regardless of the angle of pullapplied to the clamp or of the clamps reversal, even in the handling ofthin plates. The use of the bell crank in the leverage mechanism of thelifting clamp provides a means by which a gripping pressure is alwaysapplied when there is a pull on the shackle, since the arm of the bellcrank to which the pull or turning moment is applied is located wellwithin the body of the clamp and always inwardly with respect to theposition of the pivot point of the bell crank.

Other objects, features and. advantages of the present invention aredescribed more in detail hereinafter in connection with an illustrativeembodiment of the improved lifting clamp shown in the accompanyingdrawings forming a part of this application.

In the drawings:

Fig. 1 is an elevational view of a lifting clamp embodying the featuresof the present invention, partly in section with one of the side platesof the clamp removed, the clamp being illustrated in connection with avertical lift or pull on a vertically extending steel plate having athickness of about 2 inches, for example;

Fig. 2 is a view similar to that of Fig. 1 showing a slightly modifiedbody structure for the clamp and illustrating a vertical lift with theclamp, short leg up, gripping a horizontal steel plate having athickness which may be somewhat less than one fourth inch;

Fig. 3 is an elevational view of the clamp of Figs. 1 and 2, lookingfrom the left in Fig. 2;

Fig. 4 is a broken view similar to that of Fig. l, of a heavy dutylifting clamp constructed in accordance with the features of the presentinvention and adapted for handling plates of from two to twelve inchesthick, and for lifting loads up to tons or more; and

Fig. 5 is a broken view looking from the right in Fig. 4 showing thestructure of the lifting shackle.

Referring to Figs. 1, 2, and 3 of the drawings. the improved platelifting clamp shown therein comprises a clamp body I0 having a short legor jaw l2 and a long leg or jaw l4, spaced and facing each other toprovide a slot 16 for receiving a plate It to be gripped and lifted bythe clamp. The short jaw I2 is provided with a serrated gripping pad 26extending slightly into the slot I6 and facing the longer leg or jaw l4.

The body ID of the clamp includes a pair of spaced side plates 22 and24, which are held in spaced relation by spacing blocks 26, 28, and 3!]-and riveted together by means of rivets 32. The spacing blocks 26 and 28may have a thickness equal to the space between the plates or may have athickness of only half the distance between the plates, the separatehalves being integral respectively with the plates "22 and 24, so thatthey engage each other when the plates are riveted together. The spacer30 preferably comprises a spacer ring which also serves as a stop forthe gripping cam of the clamp, but it may have a larger area than thatshown and may be of the same structure as the spacing portions 26 and:28, and also extend to the adjacent margin of the clamp.

The longer jaw 14 includes and houses a gripping cam 34, the lowerportion of which is pivoted on a pivot pin 36 located in the lowerportion of the jaw H1. The cam 34 includes an enlarged hub portionmounted between the side plates 22 and 24, while the pin 36 is of thecotter pin type held in the body of the clamp by a cotter pin 38 (Fig.3).

The leverage mechanism for actuating the serrated cam 34 into and awayfrom gripping engagement with the plate l8 includes a bell crank 40mounted between the side plates 22 and 24 in the upper portion of theclamp body and pivoted therein on a pivot pin 42 held in place by acotter pin 44. The bell crank 40 is arranged with its inside anglefacing generally toward the cam 34 and its outer arm 46 is provided withan end portion having the same thickness as the cam 34. this arm beingconnected to the cam by a pair of connecting links 48, respectivelyarranged on opposite sides of the arm 46 and gripping cam 34 and beingpivoted thereto by pivot pins 49 and 54, respectively, the edges ofwhich are each peened over into a counterbore to hold them against axialmovement as shown in Fig. 3.

The other arm 52 of the bell crank 46 is forked, as indicated in Fig. 3and is pivoted to the inner end of a connecting-lifting link 54 by meansof a pin 56 held in place in the same way as pin 5!]. Thelifting-connecting link 54 extends between the sides 5'! and 58 of aforked, twisted type lifting shackl 60 carrying a drop forged liftingring 62 adapted to receive a hook 64 normally carried by a lifting craneor other lifting apparatus. The lower end of the lifting shackle 66 ispivoted to the lifting link 54 by means of a pin 66 located intermediatethe ends of the link 54 and held in place axially in the same manner aspins 49, 59 and 56. The projecting end 68 of the link 54 extends betweenthe sides 51 and 58 ofthe forked shackle 66 and aids in keeping thelifting linkage in alignment and adds strength to the lifting shackle64, which, in addition is a forged shackle in which the opposite sidesare held together by an integral web 59. The ring 62 is preferably widerat the top than at the bottom, so that it is readily engaged by a heavyhook, such as the hook 64.

Most, if not all, parts of the clamp are of heavy forged steel and theleverage and lifting elements of thee lamp, except the ring 62, arearranged so that they readily fit Within the side walls 22 and 24, asshown in Fig. 3. For example, the cam 34 has a relatively large hubwhich fits between the plates 22 and 24, While the web of the cam isengaged on opposite sides between links 48, which also engage theopposite sides of the bell crank arm 46. The bell crank 40 includes athick hub section integral with the forked ends of the arm 52 which fitbetween the side plates 22 and 24, while the forked end of the liftingshackle 60 also fit between the side plates 22 and 24, as they span thelink 54.

Figs. 1 to 3 illustrate the structure of a clamp, particularly designedfor handling up to siX ton loads or steel plates or other articleshaving a thickness up to 2 inches in thickness. Fig. 1 shows the clampcarrying a one inch steel plate with a vertical lift and it will be seenthat the leverage applied by the pull exerts a counterclockwise torqueon the bell crank 46 so that the arm applies pressure on the links 48and cam 34 tending to rotate the cam 34 clockwise, or in a direction toincrease its grip on the plate IS. The stop 30 is located at such aposition that the cam 34 can never asssume a position where the ivot pinis in line with the pivot pins 36 and 49. Therefore, the cam 34 willalways be actuated toward a gripping position whenever pressure isapplied on the connecting links 48.

The arrow on the bell crank 40 indicatesthe application of acounterclockwise torque in the lifting operation, and thearrows on thelink 48 and the cam 34 indicate the direction of applied pressure, whilethe arrows on the link 54 and the ring 62 indicate the direction of pullin applying thecounterclockwise torque to the bell crank 40'. Assuming,for example, that the pull applied by the hook 64 is changed from thevertical position through a 90 angle to the left'in Fig. I, it will beseen that the same torque will be applied to the bell crank 40, and thatthere would be no possibility of the clamp being released from'the plate[8.

A counterclockwise torque is also applied to the bell crank 40 if it isassumed that the hook 64 and the lifting shackle 60 are swung to theright at'any angle down to the horizontal, because the pivot pin 56would always be below a line between the pivot pins 44 and 58.Furthermore, as the lifting shackle 6c is pivoted on the pin 66 to apoint approaching the horizontal, it will engage the upper end portion12 of the spacer blocking 28 which, according to the structure in Fig.1, extends up to about the height of the pivot pin 42 in the body of theclamp, or somewhat above the upper rivet 32'. If' the lifting shackle 60is swung clockwise on the pivot pin 66, it will reach a point where itcomes in contact with the spacer blocking edge i2 and will apply aleverage and a pull on the lifting link 54, so that a counterclockwisetorque. on the bell crank 40 is insured.

The clamp shown in Fig. 2 has exactly the same structure as the. clampshown in Fig. 1, except that the spacer blocking 28' does not includethe projecting portion 12 shown in Fig. 1. In, Fig.2, the spacing 28'extends only slightly above the upper rivet 32 and considerably inwardlyfrom the position of the pivot pin 42.

Fig. 2 illustrates the sure grip of'the lifting clamp'under one of themost adverse operating conditions, that is, a condition. in which theshorter jaw. I2 is on topv of a thin plate 14, about one fourth inch,and the pull on the lifting ring 62 is vertical. Even under thiscondition it will be seen that the extreme thinness of the plate 14,coupled withthe direction of pull on the clamp has not moved the pivotpin 56 into alignment with the pivot pins 42 and 66, and that,therefore, the pull on the clamp as seen in Fig. 2 is applyingacounterclockwise torque to the bell crank 48, and consequently agripping pressure on the cam 34. a

'If the pull in Fig. 2 is swung to the left, it will ,be apparent thatthe liftingtlinkage will pivot on pin 56 and increasethe torque appliedto the bell crank 46. On the other hand, if the pull applied to the,lifting linkage in Fig. 2 is'swung to the right, there may be a slightmovement of thel-ink 54 into engagement with the spacing blocking 28'but it will be insufficient to bring the pin 56 into alignment with thepivot pins42 and 66. Further swing of the pull towarclfthe right inFig.2"will cause pivoting on the pin 66 and an increase in thecounterclockv lise'torque applied to the bell crank 49.

Sometimes, after a thin plate has been lifted bya clamp, the operatordecides that he wants to turn the plate over and let it down, whichwould bring the short jaw on top. Other clamps, as explained above,under such operating conditions, have actually been disengaged and theplate allowed to fall. Such mishaps are entirely avoided by the improvedconstruction of the leverage mechanism of the clamp according to thepresent invention.

The modified form of clamp construction shown in Fig. 4 is particularlydesigned for heavy duty clamps adapted to take steel plates of from twoto twelve inches thick and weighing up to tons. This clamp hasessentially the same structure and includes the same leverage mechanismas the clamp shown in Figs. 1 to 3, but includes a modified liftinglinkage. Where the elements in Fig. 4 are the same as in Fig. 1, theyare referred to by the same numbers plus a prime.

In Fig. 4 the side plates of the clamp body It! each include an integralspacer block element 15 which extends somewhat above the level of thepivot pin 42",the body plates being held together at this point by arivet 18. The lifting linkage connected to the forked arm 52 of the bellcrank 46' includes a lifting-connecting link 86, one end of which ispivoted in the forked end 52' on the pivot pin 56', while the other endis pivoted on a pivot pin 82 in the forked end of a heavy liftingshackle 84 having an opening 86 for receiving the hook of a liftingcrane. The lifting shackle as is a very heavy forged element in whichthe upper portion is provided with an opening wider at the top than atthe bottom for receiving the hook of a lifting crane, whereas the lowerend of the shackle 84 includes. the forked side section spanning theupper end of the link 80 and pivoted thereto by the pivot pin 82. I

If the lifting clamp shown in Fig. 4 is compared with the structureshown in Fig. 1, it will be apparent that, in a lifting operation, acounterclockwise torque (as seen in Fig. 4) will be applied to the bellcrank 4t, regardless of the angle of pull on the lifting shackle 84. Ifthis shackle is swung to the left on the pivot pin 82, it will be seenthat a gripping torque-will always be applied by the bell crank 46". Thesame is true if the'lifting shackle 84- is swung to the right until theconnecting link 80 engages the spacer blocking 16, or this blocking isengaged by the lifting shackle 84.

The use of the bell crank in the clamp provides a structure such thatthe gripping clamp is always urged toward gripping position, regardlessFrom the foregoing, it will be seen that, regardless of the direction ofpull on the lifting linkage of the clamp, there will always be a torqueapplied to the bell crank in a direction such that a gripping pressurewill be applied to the cam 34, thereby preventing the release of anyplate or object during a lifting operation or during a loweringoperation.

of the direction of pull on the lifting linkage. Furthermore, the use ofhe bell crank in connection withthe. short connecting and lifting link54 or St! provides acoinpact structure, in which a part of the liftinglinkage extends into the body of the clamp and aids in its safe andefiective operation. Furthermore; the links 54 and 8t provide a meansfor connecting the lifting shackle to the arm of the bell crank so thata straight pull may bejapplied to the lifting shackle.

The bell crank of the lifting clamp shown in the drawings has aninternal angle slightly greater than 90, but it may have an angle of 90,the bell crank being preferably arranged as shown so that the arm towhich the pull is applied in a lifting operation, where a single liftinglinkage is used, extends generally toward or over the receiving slot fortheplate to be lifted.

'When the clamp grips a plate having about .7

maximum thickness'for the clamp as in Fig. 1,

the bell crank arm 52 is parallel to the connecting links 48, while inthe other extreme, Fig. 2, the arm 52 inclines inwardly in the clampbody from the position of the pivot of the bell crank.

The projecting portion 68 of the link 54 has an important function inaddition to those described above. Sometimes the cam member does notreadily release from a plate after the plate has been brought to rest.In such case the projection 68 is struck with a hammer, which applies asharp pull on the connecting links 48 to pull the cam member 34 awayfrom the plate.

What is claimed as new is:

1. In a lifting clamp including a body having spaced opposed dependingportions between which the article to be lifted is held, a gripping padon one of said depending portions facing the other depending portion,and a cam member having an arcuate article-gripping surface pivoted insaid other depending portion with its gripping surface facing toward thegripping pad, 8. bell crank pivotally mounted in said body above the cammember with its inside angle facing generally toward the cam member, aconnecting link in said body for actuating the cam member toward andaway from the gripping pad the ends of which are respectively pivoted bymeans of pivot pins to the cam member and to the arm of the bell crankextending generally toward the depending portion in which the cam memberis pivoted, and a lifting shackle connected to the other arm of the bellcrank lever for applying a torque to the bell crank and a grippingpressure of said link and cam member simultaneously with the applicationof a lifting pull on the clamp.

2. A lifting clamp as claimed in claim 1 in which the bell crank ispivoted in the body above the pivot point of the cam member.

3. A lifting clamp as claimed in claim 1 in which a slot is in the clampbody for receiving the article to be lifted, the arm of the bell crankto which the lifting shackle is connected extending generally towardsaid slot and downwardly from the pivot point of the bell crank.

4.. In a lifting clamp including a body having spaced opposed dependingportions providing a downwardly extending slot when the clamp is invertical lifting position said slot being adapted for receiving a plateor other article to be lifted, a gripping pad on one of said dependingportions facing the other depending portion across said slot, and a cammember having an arcuate article-gripping surface and pivoted in saidother depending portion opposite said slot with its gripping surfacefacing toward the gripping pad, a bell crank pivoted in the upperportion of said body with its inside angle facing generally toward saidcam member, a connecting link in said body the ends of which arerespectively pivoted to the cam member above the pivot point of the cammember and to the outside arm of the bell crank, and a lifting shackleconnected to the other lifting arm of the bell crank lever for applyinga pull thereto to effect a turning torque on the bell crank and apply agripping pressure on the connecting link and cam member, the lifting armof the bell crank being approximately parallel to the connecting linkwhen the cam member is gripping an article of about maximum thicknessfor said slot, said lifting arm extending from the pivot point of thebell crank inwardly of said pivot point when the cam member is ingripping contact with an article of approximately minimum thickness withrespect to the width of said slot.

5. A lifting clamp as claimed in claim 4. in which the said lifting armof the bell crank is forked, and a connecting link is pivoted in theforked arm and in the lifting shackle.

6. A lifting clamp as claimed in claim 5, in which the lifting shackleincludes a pair of parallel spaced legs forming a forked connection withthe connecting link pivoted therein, the pivot point being at the endsof the legs and the link pivoted therebetween including a projectingportion beyond the pivot point engaging between said legs to increasethe strength of the lifting linkage of the clamp.

'7. In a lifting clamp including a body having spaced opposed dependingportions providing a slot in which the article to be lifted is held, agripping pad on one or" said depending portions facing the otherdepending portion across said slot, and a cam member having an arcuatearticle-gripping surface pivoted in said other depending portion withits gripping surface facing toward and adapted to be moved across saidslot toward the gripping pad, a bell crank pivotally mounted in saidbody with its inside angle facing generally toward the cam member, aconnecting link in said body for actuating the cam member toward andaway from the gripping pad'the ends of which are respectively pivoted bymeans of pivot pins to the cam member and to the outwardly-exteding armof the bell crank, a lifting linkage connected to the inwardly-extendingarm of the bell crank lever and including a lifting shackle, saidinwardly-extending arm and said lifting shackle having forked ends, anda connecting lift link pivoted to said last-mentioned arm and to saidlifting shackle respectively in the forked ends thereof.

3. A lifting clamp as claimed in claim '7 in which the clamp bodyincludes a pair of spaced plates between which the cam member, theconnecting link, the bell crank, the lift link and a portion of thelifting shackle are mounted and operate.

9. A lifting clamp as claimed in claim 7 in which said lift link ispivoted at a point intermediate its ends in the lifting shackle, one endportion of said lift link projecting beyond said point substantiallyintd the lifting shackle and serving to stiffen the lifting linkage withrespect to any side pull on the clamp.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,011,660 Strathern Dec. 12, 1911 2,284,006 McLellan May 26,1942 2,393,101 Gardner Jan. 15, 1946

